Thermoplastic polyester resins are well known materials which, due to their many advantageous physical properties, find use as engineering resins in many commercial and industrial applications. Such resins, for example, exhibit excellent properties of toughness, flexibility, impact strength, chemical resistance, and heat resistance. Typical polyester resins are prepared from a dihydric alcohol or a polyglycol ether and a dicarboxylic acid or chemical equivalent thereof. Closely related polycarbonate resins are prepared from a dihydric phenol and phosgene or a phosgene procursor, and, if an aromatic dicarboxylic acid is also included, the resin obtained will be a poly(ester carbonate). If a wholly aromatic dihydric phenol and a wholly aromatic dicarboxylic acid or derivative are reacted, the product will be a special type of polyester known as a polyarylate resin.
These resins have been commonly blended with other resins to produce blends having various modified properties. For example, blends of these resins with second and even third thermoplastic resin can lead to blends which not only have the above mentioned properties but additionally have excellent properties for which such thermoplastic resins may not ordinarily be recognized, such as chemical resistance, hydrolytic stability, resistance to brittle failure and gas barrier properties.
For some important applications, e.g. automotive parts, it is important that such resins have enhanced chemical resistance to aggressive solvents, for example, acetone, aromatic solvents, gasoline, and the like, to a degree which may not be necessary in most other applications. In the inventions of Ser. Nos. 812,433 and 117,246 the necessary levels of solvent resistance in combination with excellent levels of other necessary properties, are achieved by use of certain blends of polycarbonate, poly(ester carbonate), polyarylate or polyester with polyamides. Although such blends exhibit many desirable properties of such resins including excellent chemical resistance, ductility, and resistance to brittle failure, and high gas barrier properties, they have one drawback, however, and that appears to be a certain lack of compatibility, as evidenced by delamination of articles molded from such blends.
In the above mentioned application Ser. No., 117,245, block copolymers comprising polyamide segments and polyester segments are disclosed to be useful per se as molding resins and as blending resins with other thermoplastics.
Such polyamide-polyester block copolymers now, surprisingly, have been found to significantly improve the compatibility of blends of polyamides with polyesters, polycarbonates, poly(ester carbonates) and polyarylates. Molded articles containing an effective amount of the polyamide-polyester block copolymer including those having an effective content of a rubbery impact modifier have much less tendency to delaminate and they exhibit high notched Izod impact values, especially in modified versions.
The present invention, therefore, provides blends containing polyamides and thermoplastic resins which otherwise exhibit the desirable properties of such resins, without evidence of incompatibility.